Rechargeable batteries such as batteries made up of many lithium-ion cells can be used in many applications, including for example, electric propulsion vehicle (“EV”) and hybrid electric vehicle (“HEV”) applications. Lithium-ion batteries in electric or hybrid electric vehicles typically generate large amounts of heat that needs to be dissipated, therefore these types of batteries or battery systems need to be cooled to extend their service life.
Liquid cooled heat exchangers, such as cold plate heat exchangers, can be used to manage the thermal load of the batteries used in these types of battery systems. Cold plate heat exchangers are heat exchangers upon which a stack of adjacent battery cells or battery cell containers each housing one or more battery cells are arranged for cooling and/or regulating the temperature of a battery unit. The individual battery cells or battery cell containers are generally arranged adjacent to each other in face-to-face or surface-to-surface contact with each other to form the battery stack, the stack of battery cells or battery cell containers being arranged on top of the cold plate heat exchanger such that an end face or end surface of each battery cell or battery cell container is in surface-to-surface contact with a surface of the heat exchanger.
Temperature uniformity across the surface of battery cooling heat exchangers is an important consideration in the thermal management of these types of battery units or overall battery systems as temperature uniformity across the surface of the heat exchanger relates to ensuring that there is a minimum temperature differential between the individual battery cells in the overall battery unit. In electric and/or hybrid electric vehicle applications vehicles that have multiple battery packs of different sizes, each battery pack does not generate the same thermal load and so, in turn, the coolant flow rate to each cold plate does not necessarily need to be the same. Therefore, since each heat exchanger or cold plate in the battery system may not require the same coolant flow rate, it may be desirable to bypass some of the coolant flow away from one or more heat exchangers within the system in an effort to ensure a more uniform temperature distribution and to mitigate pressure drop within the overall system. Accordingly, heat exchangers having bypass structures incorporated therein are desirable and may be considered useful for these types of applications, in particular.